Low-Field Electron Emission Properties from Intrinsic and S-Incorporated Nanocrystalline Carbon Thin Films Grown by Hot-
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Low-Field Electron Emission Properties from Intrinsic and Nanocrystalline Carbon Thin Films Grown by Hot- Filament CVD
S-Incorporated
S. Guptaa, B. R. Weinerb, B. L. Weissb, G. Morellc , Kenyetta Johnson* and Oscar O. Oritz* a Department of Physics, University of Puerto Rico, San Juan, P O Box 23343, PR00931, USA b Department of Chemistry, University of Puerto Rico, San Juan, P O Box 23346, PR00931, USA c Department of Physical Sciences, University of Puerto Rico, San Juan, P O Box 23323, PR00931, USA *NSF-REU (CHE/9732391) summer 2000 participants. ABSTRACT Results are reported on the electron field emission properties of intrinsic and Sincorporated nanocrystalline carbon (n-C:S) thin films grown on molybdenum substrates by hotfilament CVD technique from methane-hydrogen (CH4/H2) and hydrogen sulphide-hydrogen (H2S/H2) gas pre mixtures respectively. The field emission properties for the S-incorporated films were investigated as a function of substrate temperature (TS). Lowest turn-on field was observed at 4.5 V/µm for one of the sample, which was grown at 900 oC, demonstrating the effect of sulfur addition. The S-incorporation also causes microstructural and structural changes, as characterized with ex situ techniques such as SEM, AFM and Raman spectroscopy (RS). Sassisted films show smoother surfaces and finer-grained than those grown without it. The electron field emission properties of S-assisted films is also compared to the film grown without it (intrinsic) at a particular deposition temperature and the turn-on field was found to be almost half for the S-assisted film than for the non S-assisted film. The influence of growth temperature was also conducted and an inverse correlation was found with the turn-on field (Ec). These studies were performed in order attempt to “tailor-the-material” as a viable cold cathode material by introducing the defects and altering the electronic structure. INTRODUCTION In the field of vacuum microelectronic (VME) devices, cold cathodes as electron field emitters are potentially useful for field emission displays (FEDs) [1-3]. Recently, electron field emission (EFE) from diamond and diamond-like carbon (DLC, disordered carbon) attracted a great deal of interest that require thin film cathode and low threshold field in contrast to existing sharp metal tips for the flat panel displays (FPDs) [4-6]. In addition, DLC FED's are certainly cost-effective, in contrast to the complicated fabrication process of Spindt tips [1] and the excellent mechanical and chemical stability of diamond would result in highly reliable and stable emitters, even under extreme conditions. In spite of the fact that the original work on electron field emission from diamond was motivated by the discovery of its negative electron affinity (NEA) [7], the ease of emission from many carbon materials suggests that the NEA is not a prerequisite and may be a bonus feature. Because of the paucity of a single definite source of electron emission, it defies understanding of the EFE mechanism and more general emission
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